A square is inscribed in a right-angled triangle with legs p and q :

A square is inscribed in a right-angled triangle with legs p and q, and has a common right angle the diagonal of the square is given by
(a) pq/(p + 2q)
(b) pq/(2p + q)
(c) sqrt.2pq/(p + q)
(d) 2 pq/(p + q)